The adenovirus E1A proteins are viral proteins which regulate viral and cellular gene expression and are involved in the transformation of rodent cells. The mechanism by which the E1A proteins carry out these functions is likely by interactions with a variety of cellular regulatory proteins. In fact a number of cellular factors which bind to the adenovirus E1A proteins are coimmunoprecipitated from cells containing the E1A proteins by monoclonal antibodies directed against E1A. Proteins with molecular weights of 300, 150, 130, 107, 105, 60 and 40 kDa respectively have been characterized and the identity of several of these proteins has been determined. The 105 kDa protein is a product of the retinoblastoma gene while the 107 kDa protein is related to the retinoblastoma gene product. The 60 kDa protein is cyclin A and the 4OkDa protein is likely TBP which is a component of the TATA protein binding complex TFIID. These results indicate that E1A interacts with cellular factors involved in controlling cellular growth and gene expression. However, the identity of several E1A-associated proteins including proteins of 300 kDa and 130 kDa remain unclear. The 300 kDa protein binds to the amino terminus of the E1A protein and has recently been demonstrated to bind to NF-kB related sequence motifs. The 300kDa protein is thought to be involved in both E1A-mediated enhancer repression and cellular transformation. The 130 kDa protein is a cellular phosphoprotein which is potentially involved in cellular transformation though little else concerning its function is known. Studies in our laboratory have focused on the regulation of cellular factors that interact with viral enhancer and TATA elements. One of these factors is a 300 kDa DNA binding protein known as PRDII-BF1 which binds to NF-kB related sequence motifs. The other factor is a 130 kDa cellular protein known as TATA modulatory factor (TMF) which binds to a number of different TATA elements. Our results indicate that both of these proteins bind to EIA and may be the previously described 3OOkDa and 130 kDa E1A associated proteins. The goals of this grant are (1) to identify the domains of PRDII-BF1 and E1A responsible for their interaction, (2) to determine whether PRDIII-BF1 is involved in E1A- mediated enhancer repression and transformation of rodent cells, (3) to identify the domains of TMF and E1A responsible for their interaction and (4) to determine whether TMF may modulate E1A transcriptional or transforming properties. These results will be important in elucidating the mechanisms by which E1A alters gene expression and induces cellular transformation.